I have installed Sitemap Generator yesterday. After a day of fine tuning the programs is working fine.
I had to set Maximum depth level to 2, and I get 4245 URLs indexed in about 4 minutes.
If I set Maximum depth level to 3, the program slows down. I can indes 100-200 URLs; if I set a higher limit (500 URLs or more), the program stalls and I get no sitemap.